Burner control apparatus



June 17, 1953 J. c. BLACKETT ETAL 2,839,132

BURNER" CONTROL APPARATUS Filed March 4, 1957 IN V EN TOR. JAMES C. BLACKETT FRED T. DEZIEL fjwl ATTORNEY United States Patent BURNER CONTROL APPARATUS James C. Blackett, St. Louis Park, and Fred T. Deziel,

Bloomington, Minn., assignors to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application March 4, 1957, Serial No. 643,720

'7 Claims. (Cl. 158-124) The present invention is concerned with an improved burner control apparatus and more particularly with a burner control apparatus which provides for checking of the proper operation of the apparatus.

A self-checking type of burner control apparatus has been proposed wherein a cycling relay is controlled in accordance with the presence of flame. The cycling relay, upon flame being established, controls the simulation of the absence of flame to thereby cause the cycling relay to continuously cycle in the actual presence of flame. The operation of the cycling relay transfers power to a continuously energized flame relay by means of a capacitor charge and discharge circuit. This circuit consists essentially of a capacitor which is first charged from a source of direct current voltage and then discharged into a continuously energized flame relay which is shunted by a second capacitor, this second capacitor maintaining the charge to thereby cause the flame relay to be continuously energized so long as the cycling relay continues to cycle at a given rate. Such an apparatus insures that the flame detector can both sense the presence of flame and the simulated absence of flame and thereby continuously checks for a component failure within the apparatus. It has been found however that the above mentioned second capacitor which shunts the continuously energized flame relay may open circuit and thereby cause the flame relay to follow the cycling of the cycling .relay. Due to the manner in which this flame relay is normally connected to components of the burner control unit, such operation is highly undesirable.

It is an object of the present invention to provide an interlock means to insure that the continuously energized flame relay of a self-checking type burner control apparatus remains de-energized in the event that the flame relay becomes de-energized subsequent to the initial energization thereof.

It is a further object of the present invention to provide an improved burner control apparatus having a cycling relay, a flame relay, an inter-lock relay, and a control relay, with the relays so inter-connected and inter-related that optimum safe operation of the controlled burner unit is achieved.

These and other objects of the present invention will be apparent to those skilled in the art upon reference to the following specification, claims, and drawing, of which The single figure is a schematic representation of the present invention.

Referring to the single figure, the reference numeral designates generally a fuel burner unit having a main burner 11, a main fuel valve 12, a pilot burner 13, a pilot fuel valve 14, an ignition transformer associated with the pilot burner 13, and a condition or flame sensing means in the form of a photo-emissive cell 16. The fuel burner unit is controlled such that the pilot valve 14 and the ignition transformer 15 are initially energized to establish a flame at the pilot burner 13. This pilot flame is then detected by the photocell 16 and the main 2,839,132 Patented June 17, 1958 valve 12 is energized to pass fuel to the main burner 11,

this fuel being ignited by means of the pilot flame at the I pilot burner 13.

The photo-emissive cell 16 includes an anode 17 and a cathode 18 and upon the cathode 18 being subjected to radiation from flame at the burner unit 10, electrons are liberated therefrom and these electrons pass from the cathode 18 to the anode 17, upon there being a positive voltage applied to the anode 17. The photocell 16 is connected to a condition detecting means in the form of a flame detector designated generally by means of the reference numeral 19. This flame detector includes first and second electron valves or discharge devices 20 and 21 and likewise includes a cycling relay 22 having a winding 23. As will be described, upon photocell 16 sensing the presence of flame at the burner unit 10, relay 22 cycles between an energized and ade-energized condition. A flame relay 24 having a winding 25 is provided and this flame relay is continuously energized in response to the cyclic energization of relay 22.

The improved burner control apparatus likewise includes a control relay 26 having a winding 27 and an inter-lock relay 28 having a winding 29. The control relay 26 is energized in response to a call for operation of the fuel burner unit 10 as evidenced by operation of a switching controller designated by the reference numeral 30. The inter-lock relay 28 has its switch means disposed in the initial energizing circuit of both the control relay 26 and the flame relay 24 to provide for starting inter-lock of both of these relays.

Discussing the relays more in detail, the cycling relay 22 is provided with movable switch blades 31 and 32 which are biased, by means not shown, to engage stationary contacts 33 and 34 respectively upon the winding 23 of this relay being de-energized. Upon energization of winding 23, movable switch blade 32 disengages stationary contact 34 and movable switch blade 31 disengages stationary contact 33 and moves into engagement with stationary contact 35. Referring now to the flame relay 24, this relay is provided with movable switch blades 36, 37, 38, and 39. The switch blades of flame relay 24 are biased to the position shown on the single figure wherein switch blade 37 engages stationary contact and switch blade 39 engages stationary contact 41. Upon energization of winding 24, the movable switch blades 36 and 38 move into engagement with sta tionary contacts 42 and 43 respectively, and the switch blades 37 and 39 disengage contacts 40 and 41 respectively and move into engagement with contacts 44 and 45 respectively. The control relay 26 is provided with a pair of movable switch blades designated by the reference numerals 46 and 47. These switch blades are biased to the positions shown when the relay winding 27 is de-energized. Upon energization of winding 27, the switch blades 46 and 47 move into engagement with the stationary contacts 48 and 49 respectively. The inter-lock relay 28 is provided with movable switch blades 50, 51 and 52. In the de-energized condition of winding 29, the switch blades 50 and 51 are biased to engage stationary contacts 53 and 54 respectively. Upon energization of winding 29, movable switch blade 52 moves into engagement with a stationary contact 55, movable switch blade 51 disengages contact 54, and

r movable switch blade 50 moves into engagement with a stationary contact 56 and then disengages contact 53 with an overlapping action.

It is customary in a burner control apparatus to provide a safety cutout means and such a means is designated by the reference numeral 57. This safety cutout means includes a normally closed switch 58 which is latched in this position by a bimetal 59 having an actuating heater 60 associated therewith. As indicated, the upper end of bimetal 59 moves to the right upon energization of the actuating heater 60 and thereby causes the switch 58 to assume its open position. In order to reset the safety cutout means 57 to its initial position, it is necessary to first allow the bimetal 59 to cool and second, to manually depress pushbutton 61 to reset the parts to the position shown.

Referring now in detail to the flame detector 19, this apparatus receives its energizing voltage from a transformer 62 having a tapped primary winding 63, a first tapped secondary winding 64 and a second secondary Winding 65. The secondary winding 65 provides filament voltage for the discharge devices 20 and 21 and for a further discharge device 66. a

The discharge devices 20 and 21 are provided each with'an anode, designated 67 and 68, a control electrode, designated 69 and 70, and a cathode, designated 71 and 72.

The discharge device 26 is connected in controlling relation to the discharge device 21. This can be seen by tracing the current flow circuit of discharge device 20 from the lower tap of secondary winding 64 through conductor 73, cathode 71, anode 67, conductor 74, resistor 75, and conductors 76 and 77 to the tap 78 of secondary winding 64. When discharge device 20 is conductive, as it is in the absence of flame at the burner unit 10, a voltage is developed across resistor 75 such that the upper terminal is negative with respect to the lower terminal. The upper terminal of resistor 75 is connected to the control electrode 70 of discharge device 21 and the lower terminal of this resistor is connected to the cathode 72. The voltage across resistor 75 due to the conduction of discharge device 20 biases discharge device 21 to cutoff. As will be explained in greater detail, upon discharge device 26 being cutoff due to a flame being established at the burner unit 10, current no longer flows in the above traced circuit and the discharge device 21 is rendered conductive. The current conducting path for discharge device 21 can be traced from the tap 78 through conductor 77, cathode 72, anode 6S, conductor 79, winding 23 of relay 22, and conductor 80 to the upper terminal of secondary winding 64. Therefore it can be seen that when the discharge device 21 is conductive, the relay 22' is energized.

Referring now to the manner in which the photocell 16 controls the flame detector 19 and particularly the input of discharge device 20, the current flow circuit for photoelectric cell 16, which exists when flame is present at the burner unit 10, can be traced from the lower terminal of secondary winding 64 through conductors 73, 80, S1, 82, and 83 to the cathode 18 of the photocell 16 andfrom the anode 17 through conductors 84 and 85 to the parallel connected capacitor 38 and resistor 87 and then through conductors 36, 76 and 77 to the tap 78 of secondary winding 64. This above traced current flow charges capacitor 88 such that the right hand electrode thereof is negative with respect to the left hand electrode. The charge on capacitor 88 is distributed to a further capacitor 89 by means of a circuit which can be traced from the right hand electrode of capacitor 88 through conductors 85 and 90, contact 34 and switch blade 32 of relay 22, conductor 91, resistor 92, capactior 89 connected in parallel with resistor 94, conductors 8d and 73, the lower terminal of transformer secondary winding 64, secondary winding tap 78, and conductors 77, 76 and 86 to the left hand electrode of capacitor 88. This above traced circuit causes the charge on capacitor 88 to be distributed to capacitor 89 and to cause the upper electrode of capacitor 89 to be charged negative with respect to the lower electrode. The negative upper electrode of capacitor 89 is connected to the control electrode 69 of discharge device 20 and the lower electrode of this capacitor is connected to the cathode 71. Therefore, upon the photoelectric cell 16 sensing flame at the burner unit 10, the capacitor 38 is charged as above described and the charge on capacitor 88 is distributed to capacitor 89 to thereby cause discharge device 20 to be cutoff. Also, as above described, this in turn causes discharge device 21 to be rendered conductive to thereby energize the winding of relay 22.

However, the above traced charging circuit for capacitor 88 due to the photocell 16 sensing flame at the burner unit 10 includes the contact 34 and the switch blade 32 of relay 22;. Upon relay 22 becoming energized this circuit is broken and the charge on capacitor 89 is dissipated through resistor 94. The charging circuit for capacitor 88 continues to be effective to maintain a charge on this capacitor. However, after a time period the charge on capacitor 89 decreases to the point where discharge device 20 is again rendered conductive to thereby render discharge device 21 non-conductive. This in turn deenergizes the winding of relay 22 and switch blade 32 once again engages contact 34 to thereby re-establish the charging circuit for capacitor 89. In this manner, ca-

pacitor 89 is once again charged to cause the winding of relay 22 to again be energized. From the above description it can be seen that so long as photocell 16 continues to sense a flame at the burner unit it), the relay 22 cycles between its energized and its tie-energized con- 1 dition.

The cycling of relay 22 causes its movable switch blade 31 to move between the contacts 33 and 35. This action causes a capacitor 96 to be charged from a source of direct current voltage in one position of the switch blade 31 and for the then charged capacitor 96 to be discharged through the Winding 25 of flame relay 24.

the relay 22 in the, energized position, capacitor 96 is connected across capacitor 97 through a circuit which.

can be traced from the lower electrode of capacitor 97 through conductor 96, contact 35 and switch blade 31, resistor 99, capacitor 96, and conductors 100, 191, 82, 81 and to the upper electrode of capacitor 97. This 96 is now connected to the winding 25 of the flame relay 24. This can be seen by tracing a circuit from the lower electrode of capacitor 96 through conductor 160, Winding 25, conductor 103, contact 54 and switch blade 51, conductors 104 and 105, resistor 106, contact 33 and switch blade 31, and resistor 99 to the upper electrode of capacitor 96. A further capacitor 107 is provided and this capacitor is connected across the winding 25 of the flame relay 24. The charge on capacitor 96 is thereby distributed to charge capacitor 107 and to also energize the winding of flame relay 24. It is immediately recognized that so long as the cycling relay 22 continues to cycle to thereby alternately charge capacitor 96 and then discharge this capacitor into capacitor 107 and winding 25, winding 25 of the flame relay remains continuously energized.

It is apparent from the above traced energizing circuit for Winding 25 that in order for the flame relay 24 to be initially energized it is necessary that the interlock relay 28 be in its de-energized condition. The maintaining circuit for winding 25, however, includes switchmeans of the flame relay itself, namely switch blade 36 and contact 42, and therefore once the flame relay 24 is energized it is no longer necessary for the inter-lock relay 28 to remain in its de-energized position. However, should the flame relay 24 become de-energized at some later time, it is again necessary that the inter-lock relay 28 be in its de-energized position before the flame relay 24 can be re-energized.

More specifically, diode discharge device 66 is connected to the secondary winding 64 of transformer 62 to form a source of direct current voltage at capacitor 97. Considering Operation Referring now to the overall operation of the improved burner control apparatus, the apparatus as disclosed is in the standby condition. That is, the power line conductors 108 and 109 are connected to a source of alternating current voltage, not shown. The controller 30 is in an open circuit position, as it is when there is no need for operation of the burner unit 10. The main valve 12, pilot valve 14, and ignition transformer 15 are de-energized. The primary winding 63 of transformer v62 has electrical energy applied thereto from a circuit which can be traced from power line conductor 108 through conductor 110, primary winding 63, conductors 111 and 112, safety cutout switch 58, and conductor 113 to power line conductor 109. Since there is no flame at the burner unit 10, the cycling relay 22 and the flame relay 24 are both de-energized. Also, the control relay 26 and the inter-lock relay 28 are de energized.

If it is now assumed that a call for operation of the burner unit is indicated by the controller 30 closing its switch, the control relay 26 is energized through a circuit which can be traced from power line conductor 108 through controller 30, conductors 114 and 115, winding 27, conductor 116, contact 53 and movable switch blade 50 of inter-lock relay 28, conductors 117 and 118, switch blade 37 and contact 40 of flame relay 24, conductor 119, safety cutout actuator 60, conductor 120, the lower portion of the primary winding 63 of transformer 62, conductors 111 and 112 safety cutout switch 58, and conductor 113 to the other power line conductor 109. From this above traced circuit it can be seen that in order for control relay 26 to be energized, the inter-lock relay 28 must be de-energized and the flame relay 24 must be tie-energized.

Energization of control relay 26 causes movable switch blade 46 to move into engagement with contact 48. This completes an intermediate energizing circuit for the control relay 26. This intermediate energizing circuit does not include the actuator 60 of the safety cutout device and the circuit can be traced from the power line conductor 108 through controller 30, conductors 114 and 115, winding 27, conductor 116, contact 53 and switch blade 50, conductors 117 and 121, contact 48 and switch blade 46 of relay 26, conductors 122, 123 and 112, safety cutout switch 58, and conductor 113 to the other power line conductor 109. It will be noted that this intermediate energizing circuit still requires that the inter-lock relay 28 be in its de-energized condition. I

The switch blade 46 and contact 48 of control relay 26 also complete a further energizing circuit for the actuating heater 60 of safety cutout device 57. This energizing circuit can be seen by tracing a circuit from the lower terminal of the primary winding 63 through conductors 111, 123 and 122, switch blade 46 and contact 48, conductors 121 and 118, switch blade 37 and contact 40 of flame relay 24, conductor 119, actuating heater 60, and conductor 1% to the tap of the primary winding 63. From this circuit it can be seen that the actuating heater 60 of the safety cutout device 57 remains continuously energized from the time the controller 30 first calls for operation of the burner unit 10 until flame is sensed at the burner unit 10 to thereby energize the flame relay 24. The initial energizing of the actuating heater 60 is accomplished by placing the actuating heater in series with the control relay 26 to thereby insure that the control relay may not be energized unless the actuating heater 60 has electrical continuity. Once the control relay 26 is energized, the above traced circuit is completed to maintain the actuator of safety cutout device 57 energized until flame is detected at the burner unit 10.

Energization of main relay 26 also causes movable switch blade 47 to engage contact 49. A circuit is now completed to energize the pilot valve 14 and the vignition transformer 15. The energizing circuit for the pilot valve can be traced from the power line conductor 108 through controller 30, conductors 114 and 124, contact 49 and switch blade 47, conductors and 126, pilot valve 14, conductors 127, 128 and 129 to the other power line conductor 109. The energizing circuit for the ignition transformer 15 can be traced from power line conductor 108 through controller 30, conductors 114, and 124,

contact 49 and switch blade 47, conductors 125 and 130,

24 is energized and the ignition transformer 15 is turned fuel is ignited to establish a flame at the pilot burner. Photocell 16 senses the presence of flame at the pilot burner, and as above described, the cycling relay 22 is caused to continuously cycle so long as photocell 16" continues to detect the presence of this flame. The flame relay 24 is continuously energized so long as the cycling relay 22 continues to cycle. Here again, it should be noted that the initial energizing circuit of the flame relay requires that the switch 51-54 controlled by the interlock relay be in a closed circuit condition, that is the inter-lock relay 28 must be de-energized. However, upon flame relay 24 assuming its energized position, the switch 36-42 controlled by the flame relay maintains the flame relay energized independent of the condition of energization of the inter-lock relay 28.

Reviewing the operation of the inter-lock relay 28 to this point in the operation of the apparatus, switch means of this relay control the initial energizing circuit for the control relay 26 and for the flame relay 24 thereby preventing energization of either of these relays unless the inter-lock relay 28 is de-energized. more, the intermediate energizing circuit for the control relay includes the switch means of the inter-lock relay 28 in the deenergized position and at this point in the operation of the apparatus it is likewise necessary for the inter-lock relay 28 to be de-energized in order for the control relay 26 to remain energized.

The next phase of the operation of the improved burner control apparatus is accomplished upon the flame relay 24 being energized in response to flame at the pilot burner 13. Summarizing the operation of the switch means of flame relay 24, the switch 36-42 completes a holding circuit for the flame relay 24 which is independent of the state of energization of the inter-lock relay 28. The switch 37-40 in opening opens the energizing circuit for the safety cutout device heater 60 and the switch 37-44 in closing completes a holding circuit for the control relay 26 which is independent of the state of energization of the inter-lock relay 28. The switch 38-43 completes an energizing circuit for the inter-lock relay 28. The switch 39-41 in opening deenergizes the ignition transformer 15 and the switch 39-45 in closing completes an energizing circuit for the main valve 12.

Discussing the above in greater detail, since a flame is now established at the burner unit 10, it is no longer necessary to maintain the safety cutout device actuator 60 energized. The opening of the switch 37-40 by energization of the flame relay 24 accomplishes this result. The closing of the switch 37-44 by energization of the flame relay completes a holding circuit for the control relay 26 which can be traced from the power line conductor 108 through controller 30, conductor 114, winding 27, conductors 116, and 141, contact 44 and switch blade 37, conductor 118, contact 48 and Upon Fuel is now supplied to the pilot burner 13 and this Further- I switch. blade, 46, conductors I22, 123 and 112, safety cutoifswitch; 58, and conductor 113 to the other power line conductor 109. From this above traced circuit it can be seen that the. energization of the control relay 26. is now directly controlled by the flame relay 24 by switch, 37-44. so that in the event there is a subsequent flame failure at the burner unit 10, the flame relay in responding to this flame failure and becoming deenergized immediately de-energizes the control relay 26 and thereby immediately de-energizes the fuel burner unit 10 -to thereby provide for fast shutdown of the burner unit 10.

With the flame established at the pilot burner 13, it is, now possible to de-energize ignition transformer and to open the fuel valve 12 for the main burner 11. This is accomplishedby the switch blade 39 of the flame relay disengaging contact 41 and moving into engage ment with contact 45. The energizing circuit for the main fuel valve, 12 can be traced from power line conductor 108 through controller 36, conductors 114 and 124, contact 49. and switch blade 47, conductors 125 and 130, switch blade 39 and contact 45, conductor 15%), main fuel valve 12, and conductor 129 to the power line conductor 109. With. the energization of the main fuel valve 12, fuel passes to the main burner 11 and is ignited by the pilot flame present at the pilot burner 13.

Energization of the flame relay 24 also causes energization .of the inter-lock relay 28. This energizing circuitv can be traced from power line conductor 1% through controller 30, conductors 114, 115 and 164), winding 29, conductor 161, switch blade 38 and contact 43, conductors 162 and 140, contact 53 and switch blade 50, conductors 117 and 121, contact 48 and switch blade 46, conductors 122, 123 and 112, safety cutout switch 58, and conductor 113 to the power line conductor 109. The switch means of the inter-lock relay 23 now moves from the de-energized to the energized position.

The switch 50-56 of the inter-lock relay operates in an overlapping fashion with the switch 56-53. That is, the switch 50-56 makes contact before the switch 50-53 opens. The switch 50-56 is in an intermediate energizing circuit for the inter-lock relay 28 and is provided to insure proper operation of the inter-lock relay 2%. This intermediate energizing'circuit can be traced from power lineconductor 108 through controller 30, conductors 114, 115 and 160, winding 29, contact 56 and switch blade 50, conductors 117 and 12]., contact 48 and switch blade 46, and conductors 122, 123 and 112, safety cutout switch 58, and conductor 113 to power line conductor 1113. The opening of switch 50-53 opens the initial energizing circuit for the control relay 26. However, as above described, this control relay 26 is now maintained energized through the switch 44-37 controlled by the flame relay 24 and the switch 48-46 controlled by the control relay 26.

The opening of the switch 51-54 by energization of the inter-lock relay 28 opens the initial energizing circuit for the flame relay 24. However, as above described the flame relay 24 is maintained energized through the switch 36-42 controlled by the flame relay. Referring more specifically to the functioning of this portion of the apparatus, it will be remembered that the cycling relay 22 is effective to cause the capacitor 96 to be alternately charged from capacitor 97 and to then be discharged into the winding of the flame relay 24 and into the capacitor 107 connected in parallel with the winding 25. Capacitor 107 functions to maintain the flame relay 24. energized during that period of the cycle in which the cycling relay 22 is energized and the capacitor 96 is being charged. It has. been found that an unsafe condition may arise if the capacitor 107 becomes ineffective, such as if it were disconnected from the apparatus. In this case, the flame relay 24 follows the cycling relay 22 and becomes itself a cycling relay. The flame relay 24 by means of the switches 39-41 and 39-45 controls the operation of the burner unit 10 and the cycling of this relay alternately causes the main valve 12 to be opened and then the ignition transformer 15 to be energized. Such operation can produce an explosion at the burner unit 10. However, such cycling of the flame relay 24 upon the capacitor 107 becoming ineffective is prevented by the circuitry of the present apparatus since the first time the flame relay 24 is de-energized, the switch 36-42 controlled by this relay opens and the switch 51-54 controlled by the inter-lock relay 28 remains open to prevent re-energization of the flame relay 24. Such a construction provides for completely safe operation of the fuel burner unit 10 since not only does the apparatus provide a continuously self-checking arrangement but also provides an arrangement including switches 51-54 and 36-42 which prevents re-energization of the flame relay 24 once the flame relay is de-energized.

Referring again to the operation of the switch means of the inter-lock relay 28, energization of this relay causes the switch 52-55 to be closed and this completes a holding energizing circuit for the interlock relay 28. This holding energizing circuit can be traced from power line conductor 108 through controller 30, conductors 114, and 160, winding 29, conductor 170, contact 55 and switch blade 52, conductor 171, 123 and 112, safety cutout switch 58, and conductor 113 to the power line conductor 109. From this above traced circuit it can be seen that the inter-lock relay 28 remains ener gized under the sole control of the controller 30 and of the safety cutout switch 58.

The operation of the improved burner control apparatus has now been explained from the standby to the run position of the apparatus. In the run position, the control relay 26 is energized, the inter-lock relay 28 is energized, the valves 12 and 14 are energized, the flame relay 24 is continuously energized and the cycling relay 22 is energized in a cyclic manner, and the ignition transformer 15 and actuating heater 60 of' the safety cutout device 57 are both de-energized' in response to the photocell 16 sensing the presence of flame at the burner unit 10.

If it is assumed for the moment that a flame failure now occurs, photocell 16 senses the absence of flame and the photocell is no longer effective to complete a charging circuit for the capacitor 88. Therefore, the capacitor 89 discharges and remains discharged to there by cause discharge device 20 to remain conductive and discharge device 21 to remain nonconductive, therebyde-energizing cycling relay 22 and causing this relay to remain de-energized. As a result thereof, capacitor 89 no longer is periodically charged and then discharged into the flame relay 24 and as a result thereof flame switch 37-44 controlled by the flame relay opens the relay 24 is de-energized.

Upon flame relay 24 becoming de-energized, the holding energizing circuit for the control relay 26 and this relay then becomes de-energized to immediately de-energize the pilot valve 14 and the main valve 12. As has been pointed out, once the flame relay 24 is deenergized it can not be re-energized due to the fact that its switch 36-42 and the switch 51-54 controlled by the inter-lock relay 28 are both open.

Since a flame failure has occurred it is now necessary to energize the actuating heater 60 of the safety cutout device 57. This is accomplished by the closing of the switch 37-40 controlled by the flame relay 24. This energizing circuit can be traced from the lower terminal of the transformer primary winding 63 through conductors 111, 123 and 171, switch blade 52 and contact 55, conductors 170, contact 56 and switch blade 50, conductors 117 and 118, switch blade 37 and contact 40, conductor 119, actuating heater 60, and conductor 120 to the tap of the primary winding 63.

This is the condition of operation of the improved control apparatus immediately after a flame failure is detected. In this condition, the cycling relay 22 and the flame relay 24 are de-energized, all of the components of the fuel burner unit are de-energized, the control relay 26 is de-energized, the inter-lock relay 28 and the heater of safety cutout device 57 are both energized. After a time period of energization of actuating heater 60, the upper end of bimetal 59 moves to the right to cause the lockout switch 58 to open. This completely de-energizes the control apparatus, causing the interlock relay 23 to move to its de-energized condition and likewise de-energizing the primary 63 of the transformer 62. It is now necessary for the bimetal 59 of the safety cutout device 57 to cool and for the push button 61 to be manually depressed to cause the safety cutout device 57 to again assume its initial position wherein the switch 58 is closed. This again places the apparatus in the standby condition as above described.

In the event the assumed flame failure does not occur, the controller 30 is effective when satisfied to call for an end of operation of the burner unit 10. The controller 30 opens its associated switch and thereby deenergizes the control relay 26 and the inter-lock relay 28. This in turn de-energizes the burner unit 10 and causes the cycling relay 22 and the flame relay 24 to be de-energized. The apparatus is then once again in its standby condition awaiting another call for operation of the burner unit 10 as indicated by operation of the controller 30.

Consider now the phase of operation of the improved burner control apparatus wherein there is an initial failure to establish combustion. In this case, the controller 30 calls for operation of the burner unit 10 and, as above described, the control relay is energized to energize the ignition transformer and the pilot valve 14. In the event that flame is not established, the cycling relay 22 and the flame relay 24 remain in their de-energized positions. The actuating heater of the safety cutout device 57 is now energized through the above traced circuit including the switch 37-40 controlled by the flame relay and the switch 4846 controlled by the control relay. After a time period of energization of the heater 60, the switch 58 opens and once again the device is placed on safety lockout. Again it is necessary for the reset button to be depressed, after the bimetal 59 is cooled, to again place the apparatus in the standby condition.

From the above description it can be seen that we have provided an improved burner control apparatus and particularly a burner control apparatus of the self-checking type which provides for optimum safe operation of the burner unit being controlled and particularly prevents cycling of the flame relay in the event that components in the circuit controlling the flame should fail in such a manner that the flame relay tends to follow the cycling relay.

Other modifications of the present invention will be apparent to those skilled in the art and it is intended that the present invention be limited solely by the scope of the appended claims.

We claim as our invention:

1. Condition detecting apparatus comprising; condition sensing means arranged to be subjected to a given condition, signal amplifying means having input and output terminals, a first relay having an actuating winding and a normally opened and normally closed switch controlled thereby, circuit means connecting said first relay winding to the output terminals of said amplifying means, circuit means including the normally closed switch of said first relay connecting said condition sensing means to the input terminals of said amplifying means to thereby cause the winding of said first relay to alternate between an energized and a de-energized state in response to said condition sensing means being subjected to the given condition; a second relay having 10 a relay winding and a normally opened and normally closed switch controlled thereby, a third relay having an actuating winding and a pair of normally open switches controlled thereby; a source of direct current voltage, a capacitor, means controlled by said first relay arranged to cyclically charge said capacitor from said source of direct current voltage upon thewinding of said first relay being energized and de-energized in a cyclic'state, energizing circuit means for the winding of said third relay connecting the winding of said third relay to said capacitor to thereby discharge said capacitor through said third relay winding, said last mentioned circuit being initially controlled by the normally closed switch of said second relay and being maintained by a first of the normally open switches of said third relay, the actuating winding of said third relay being maintained continuously energized so long as said capacitor cyclically is charged from said direct current voltage source in response to said first relay cycling between the energized and de-energized conditions; energizing circuit means for the winding of said second relay initially controlled by the second of said normally open switches to said third relay and being maintained by the normally open switch of said second relay to thereby insure that the winding of said third relay is not re-energized in the event that a fault occurs to cause the winding of said third relay to be subsequently de-energized, and further means controlled by said third relay in response to the establishment of the given condition at said concondition to be detected, signal transmission means having an input and an output, first switching means having an actuator and a first and second switch controlled thereby, circuit means connecting said first switching means actuator to the output of said signal transmission means, circuit means controlled by the first switch of said first switching means connecting said condition sensing means to the input of said signal transmission means, said first switching means actuator being energized in accordance with the condition sensed by said condition sensing means, said actuator functioning through the first switch of said first switching means to simulate the absence of the condition and thereby cause the actuator of said first switching means to be cyclically energized and de-energized upon said condition sensing means'being subjected to the condition to be detected; second switching means having an actuator and a pair of switches controlled thereby, third switching means having an actuator and a switch controlled thereby; energizing circuit means for the actuator of said third switching means controlled by the first switch of said second switching means and the second switch of said first switching means and arranged and constructed to energize the actuator of said third switching means upon the actuator of said second switching means being deenergized and upon the actuator of said first switching means being energized in a cyclic manner; holding circuit means for the actuator of said third switching means arranged and constructed to maintain the actuator of said third switching means continuously energized so long as the actuator of said first switching means is cyclically energized and then de-energized; energizing circuit means for the actuator of said second switching means controlled by the switch of said third switching means to energize the actuator of said second switching means upon the actuator of said third switching means being energized, holding circuit means for said second switching means actuator controlled by the second switch of said second switching means to thereby maintain said second switching means actuator continuously energized to prevent re-energization of said third switching means actuator in the event that said third switching means actuator is subsequently de-energized, and control means 1,1 indicative of the presence of, the condition to be detected and, controlled by said third switching means.

3. Flame responsive means, comprising; flame sensing means arranged to be subjected to a flame, electronic amplifying means having a first and a second electronic valve, said first electronic valve being arranged in controlling relation to said second electronic valve, a first relay having a winding connected to be energized by the output of said second electronic valve, circuit means controlled by said first relay when de-energized connecting said flame sensing means to the input of said first electronic valve to thereby cause said second electronic valve to be rendered conductive upon said flame sensing means being subjected to a flame, said first relay being operative when energized to simulate the absence of flame and thereby cause said first relay winding to be de-energized; a second relay having a winding, a third relay having avwinding; a source of direct current voltage, a capacitor, circuit means controlled by said first relay arranged to alternately connect said capacitor to said source of direct current voltage and then connect said charged capacitor to energize the winding of said third relay, the initial energizing circuit for the winding of said third relay being controlled by said second relay when the winding thereof is de-energized, the maintaining circuit of' said third relay winding being controlled by said third relay upon said third relay winding being energized, energizing circuit means for the winding of said second relay initially controlled by said third relay to energize said second relay winding upon said third relay winding being energized, maintaining circuit means for said second relay winding controlled by said second relay to maintain said second relay winding energized once it is initially energized by energization of said third relay winding, said second relay thereby functioning to prevent re-energization of said third relay winding upon said third relay winding being de-energized, and further means controlled by said third relay in accordance with the presence or absence of flame at said flame sensing means.

4. A self-checking flame detector comprising: flame sensing means arranged to the subjected to a flame, an electronic amplifier having an input and an output, a first relay having an actuating winding and switch means coutrolied thereby, first relay actuating circuit means connecting said winding to the output of said amplifier, cir cuit means controlled by said first relay switch means connecting said flame sensing means to the input of said electronic amplifier, said electronic amplifier functioning to energize the actuating winding of said first relay upon said flame sensing being subjected to a flame and Said first relay switch means functioning to simuiate the absence of flame at the input of said amplifier to thereby cause said first relay actuating winding to cycle between the energized and de-energized states upon said flame sensing means being subjected to a flame; a second relay having an actuating winding and switch means controlled thereby, a third relay having an actuating winding and switch means controlled thereby; a source of direct current voltage, a capacitor, circuit controlled by said first relay switch means arrange to cyclically connect said capacitor to said source of direct current voltage to thereby charge said capacitor and to then connect said charged capacitor through a circuit controlled by said second relay switch means to discharge said capacitor through said third relay actuating winding and thereby energize said third relay winding, said last named circuit being completed to energize said third relay actuating winding only upon said second relay actuating winding being de-energized; a maintaining energizing circuit controlled by said third relay switch means to maintain said third relay actuating winding connected to said capacitor under the control of said first relay switch means and thereby maintain said third relay actuating winding continuously energized as said l2 first relay actuating winding cycles between its energized and, de-energized states; initial energizing circuit means for said second relay actuating winding controlled by said third relay switch means upon said third relay actuating winding being energized, maintaining energizing means for said second relay actuating winding controlled by said second relay switch means to maintain said second relay actuating winding continuously energized upon being initially energized, said second relay thereby functioning to prevent re-energization of said third relay winding, and further means controlled by said third relay in accordance with the presence or absence of flame at said flame sensing means.

5. A flame detector comprising: a flame sensing means arranged to be subjected to a flame, a cycling relay having an actuating winding and switch means controlled thereby, means controlled by said cycling relay switch means upon said cycling relay actuating winding being de-energized connecting said flame sensing means in controlling relation to said cycling relay to thereby energize said cycling relay actuating winding upon a flame being sensed, said cycling relay when energized function'- ing through its switch means to simulate the absence of flame and thereby cause said cycling relay to cycle between an energized and a deenergizcd state upon said flame sensing means being subjected to a flame; an interlock relay having an actuating winding and switch means, a fiame relay having an actuating winding and switch means, a capacitor, circuit means controlled by said interlock relay switch means when said interlock relay actuating winding is de-energized connecting said flame relay actuating winding across said capacitor, further circuit means controlled by said flame relay switch means maintaining said flame relay actuating winding connected across said capacitor upon said flame relay actuating winding being energized; a source of direct current voltage, means controlled by said cycling relay switch means alternately connecting said capacitor to said source of direct current voltage to thereby supply pulses of elec trical energy to charge said capacitor and maintain said flame relay actuating winding continuously energized upon said cycling relay actuating winding cycling between the energized and de-energized state; energizing circuit means for said interlock relay actuating winding controlled by said flame relay switch means to initially energize said interlock relay actuating winding upon said flame relay actuating winding being energized, holding circuit means for said interlock relay actuating winding controlled by said interlock relay switch means to maintain said interlock relay actuating winding continuously energized once it is initially energized, said interlock relay switch means functioning to allow initial energization of said flame relay actuating winding but to maintain said flame relay actuating winding de-energized in the event that said capacitor open circuits and said flame relay actuating winding tends to follow the cycling of said cycling relay actuating winding.

6. Burner control apparatus for use with a fuel burner unit comprising; a flame detector having flame sensing means arranged to be subjected to a flame at the fuel burner unit and having a. cycling relay including a relay actuator and switch means controlled thereby, said cycling. relay switch means moving from a first to a second condition upon a flame being sensed at the fuel burner, circuit means including said cycling relay switch means arranged to simulate the absence of flame at the fuel burner unit upon said switching means moving to said second condition to thereby cause said cycling relay switch means to cycle between said first and second conditions upon a flame being present at the fuel burner unit; an interlock relay having an actuator and switch means controlled thereby, said interlock relay switch means moving from a first to a second condition upon said interlock relay actuator being energized; a flame relay having an actuator and switch means controlled thereby, a

source of direct current voltage, a capacitor, circuit means controlled by said interlock relay switch means in said first condition connecting said flame relay actuator to said capacitor, circuit means controlled by said cycling relay switch means periodically connecting said capacitor to said source of direct current voltage to periodically charge said capacitor and to thereby initially energize the actuator of said flame relay only in the event that said interlock switch means is in said first condition; a circuit controlled by the switch means of said flame relay to maintain said flame relay actuator connected to said capacitor once said flame relay actuator is initially energized, said flame relay actuator thereby remaining continuously energized as said cycling relay switch means cycles between the first and second conditions; energizing circuit means for the actuator of said interlock relay controlled by said flame relay switch means to energize said interlock relay actuator upon said flame relay actuator being energized, a holding circuit for said interlock relay actuator controlled by said interlock relay switch means in said second condition to maintain said interlock relay actuator continuously energized once it is initially energized by said flame relay switch means, said interlock relay functioning to prevent re-energization of said flame relay actuator upon said flame relay actuator being deenergizing circuit means controlled by said control relay switch means to energize said fuel burner unit upon energization of said control relay, and maintaining energizing circuit means for said control relay actuator including the switch means of said flame relay to maintain said control relay and thereby said fuel burner unit energized upon said flame relay actuator remaining energized in response to the presence of flame at the fuel burner unit.

7. In combination; cycling relay means having switch means and constructed and arranged to cycle between an energized and a de-energized state in accordance with a given condition; a direct current source of voltage, a first capacitor, a second capacitor, further relay means having switch means, interlock relay means having switch means; circuit means controlled by said cycling relay switch means to alternately connect said first capacitor to said source of voltage to change said first capacitor and then connect said charged first capacitor to said second capacitor, said second capacitor having a charge maintained thereon so long as said cycling relay switch means continues to cycle; initial circuit means controlled by said interlock relay switch means connecting said further relay means to said second capacitor, maintaining circuit means controlled by said further relay switch means connecting said further relay means to said second capacitor; initial circuit means controlled by said further relay switch means connecting said interlock relay means to a source of voltage, and maintaining circuit means controlled by said interlock relay switch means connecting said interlock relay means to the source of voltage.

No references cited. 

